What Is Asbestos?

Asbestos, also known as "asbestos", is a commercial term referring to silicate mineral products with high tensile strength, high flexibility, chemical and thermal erosion resistance, electrical insulation, and spinnability. It is a general term for natural fibrous silicate minerals. There are 6 minerals in 2 categories (including serpentine asbestos, amphibole asbestos, an asbestos asbestos, amphibole asbestos, iron asbestos, tremolite asbestos, etc.). Asbestos is composed of fiber bundles, which in turn are composed of very long and thin fibers that can be separated from each other. Asbestos has high fire resistance, electrical insulation and thermal insulation, and is an important fireproof, insulating and thermal insulation material. However, because asbestos fibers can cause diseases such as asbestos lung and pleural mesothelioma, many countries have chosen to completely ban the use of this dangerous substance.

Asbestos is also known as "asbestos fiber", a general term for certain silicate minerals that can be split into filaments rich in elastic fibers. Chemical formula: 3MgO · 2SiO ₂ · 2H ₂ O, it is fibrous, greenish yellow or white, white when split into floc, silky luster, fiber is elastic, asbestos has acid resistance, alkali resistance and heat resistance. Bad conductor of electricity. Longer fibers are used to make fire-resistant textiles, such as asbestos rope, asbestos tape, asbestos cloth, etc .; shorter fibers are used to make asbestos cement products, asbestos sound insulation materials, asbestos insulation materials (asbestos magnesium carbonate insulation powder), and low Insulation materials for voltage appliances. Asbestos generates a large amount of dust during the mining and use process, which has harm to the human body in various aspects. Attention should be paid to strengthening protection. ^[2]

Asbestos has long been used for weaving fabrics. Asbestos has high fire resistance, electrical insulation and thermal insulation, and is an important fireproof, insulating and thermal insulation material. There are nearly 3,000 asbestos products or products containing asbestos. It is mainly used in mechanical transmission, braking, heat preservation, fire prevention, heat insulation, anticorrosion, sound insulation, insulation, etc. Among them, the more important are automotive, chemical, electrical equipment, construction and other manufacturing sectors.

Human use of asbestos has proven to date back

The main types of asbestos are:

(1) Serpentine asbestos. Also called fiber serpentine or chrysotile. It is widely distributed in nature. Generally called asbestos refers to serpentine asbestos. It is a fibrous crystal of serpentine, accounting for 95% of the total asbestos output. The chemical formula is 3MgO · 2SiO ₂ · 2H ₂ O, the theoretical content of MgO is 43.46%, SiO _{2 is} 43.50%, and H ₂ O is 13.04%. Before being decomposed, it is green, yellow, gray, white and other colors, with silk or pearl luster, and it is off-white after decomposition. The fiber length is generally 1-20cm, and the longest can be more than 200cm.

(2) Hornblende type asbestos. Including blue asbestos, iron asbestos, amphibole asbestos, tremolite asbestos, ascites asbestos and many other species. Its iron and sodium content is much higher than serpentine asbestos. It has good acid resistance and corrosion resistance, and has many special uses.

(3) Pyrophyllite asbestos. It is an aluminosilicate of iron and calcium, and the fiber length is short, most is 0.5 to 1cm. The fiber has good fission property and poor bending resistance.

(4) brucite asbestos. The fibrous variant of brucite mineral has a chemical composition of Mg (OH) ₂ .

Different types of asbestos, physical and mechanical properties and

According to USGS

China's chrysotile asbestos standard system was established with reference to adopting the standards of advanced countries in the world and combining its own actual national conditions. Not only the detailed inspection methods and determination methods are specified, but also detailed inspection equipment parameters are determined.

In 1961, China issued a reference

95% of asbestos used in the world is chrysotile, whose fibers can be split into very fine elementary fibers with excellent spinning properties. Blue asbestos and iron asbestos account for less than 5% of total asbestos consumption and are mainly used in shipbuilding. Anthracite asbestos is similar

Because asbestos fibers can cause diseases such as asbestos lung and pleural mesothelioma, many countries have chosen to completely ban the use of this dangerous substance, and some other countries are examining the dangers of asbestos. Therefore, the phenomenon that asbestos nets are still used in China's junior and senior high school chemical laboratories is very worrying.

Asbestos asbestos pollution

About 95% of the asbestos used in the world is chrysotile. Its fibers can be split into very fine element fibers. About 10 grams of asbestos fibers are released into the environment for each ton of asbestos consumed in the industry. One kilogram of asbestos contains about one million elementary fibers. Element fibers are generally 0.5 microns in diameter and less than 5 microns in length. They can be suspended in the atmosphere and water for weeks and months, causing continuous pollution. Studies have shown that asbestos-related diseases are widespread in a variety of industrial occupations. Such as asbestos mining, processing and use of asbestos or asbestos-containing materials in various industries (construction, ship and car repair, metallurgy, textiles, mechanical and electrical engineering, chemical, agriculture, etc.)

The US Environmental Protection Agency has restricted the use of some asbestos products, such as the 1972 ban on asbestos fiber-containing refractory coatings.

During 1980-2003 in Germany, asbestos-related occupational diseases caused 12,000 deaths. As many as 2,000 people die from asbestos in France each year. The United States reported nearly 20,000 asbestos cases during the period 1990-1999.

In 1998, the World Health Organization reaffirmed the carcinogenic effects of serpentine asbestos, particularly its risk of causing mesothelioma, and continued to call for the use of this asbestos substitute. Most EU member states have banned the use of this type of asbestos (all member states must ban all asbestos use by 2005).

At present, there is no quality standard for indoor air asbestos concentration in any country. In the United States, the standard for asbestos in water is 0.05 micrograms per liter, and the states in Connecticut and New York state that the maximum allowable amount of asbestos in the atmosphere is 30 fibers per cubic meter (30-day average) and 27 fibers per cubic meter.

China: The threshold value for chrysotile asbestos in the workshop air is 2 fibers / cubic.

Asbestos carcinogenicity

Asbestos carcinogenicity

Asbestos itself is not poisonous. Its greatest harm comes from its dust. When these fine dusts are inhaled into the human body, they will attach and deposit in the lungs, causing lung diseases. Asbestos has been identified as a carcinogen by the International Cancer Research Center Thing.

On the other hand, extremely small asbestos dust is scattered into the air, and after being inhaled into the human lungs, it can easily induce lung diseases such as lung cancer after a latency period of 20 to 40 years. This is the problem of asbestos pollution that has received varying degrees of attention in countries around the world. In Europe, it is predicted that by 2020, 500,000 patients will die from lung cancer caused by asbestos pollution. In Japan, 100,000 people are projected to die by 2040.

Exposure to (as long-term inhalation) a certain amount of asbestos or elementary fibers can cause the following diseases:

(1) Lung cancer and gastrointestinal cancer;

(2) Mesothelial cancer-pleural or peritoneal cancer;

(3) Asbestosis-scarring of lungs due to fibrosis of lung tissue (asbestos lung);

(4) The symptoms of asbestos-related diseases often have a long incubation period, which may only appear after 10 to 40 years of exposure to asbestos (lung cancer generally 15 to 20 years, mesothelioma 20 to 40 years).